Chapter 1 – Computer Systems

BYU CS 345OS Overview (Chapter 1)2 CS 345 Stalling’s Chapter#Project 1: Computer System Overview 2: Operating System Overview 4P1: Shell 3: Process Description and Control 4: Threads 4P2: Tasking 5: Concurrency: ME and Synchronization 6: Concurrency: Deadlock and Starvation 6P3: Jurassic Park 7: Memory Management 8: Virtual memory 6P4: Virtual Memory 9: Uniprocessor Scheduling 10: Multiprocessor and Real-Time Scheduling 6P5: Scheduling 11: I/O Management and Disk Scheduling 12: File Management 8P6: FAT Student Presentations6

Learning Objectives Describe the basic elements of a computer system and their interrelationship. Explain the steps taken by a processor to execute an instruction. Understand the concept of interrupts and how and why a processor uses interrupts List and describe the levels of a typical computer memory hierarchy. Explain the basic characteristics of multiprocessor and multicore organization. Discuss the concept of locality and analyze the performance of a multilevel memory hierarchy. Understand the operation of a stack and its use to support procedure call and return. BYU CS 345OS Overview (Chapter 1)3

Quiz: Define the following terms Kernel BYU CS 345OS Overview (Chapter 1)4 Systems program Applications program Middleware Firmware Bootstrap program Daemon Device driver Asymmetric multiprocessing Symmetric multiprocessing

Operating System Tradeoffs Convenience vs efficiency Ease of use vs maximum resource utilization Interactive user interface vs no user view Asymmetric vs symmetric processing Single-processor vs multiprocessor systems Unicore vs multicore systems UMA vs NUMA Batch vs time sharing Logical vs physical memory Dual mode vs multimode BYU CS 345OS Overview (Chapter 1)5

Learning Objectives Describe the basic elements of a computer system and their interrelationship. Explain the steps taken by a processor to execute an instruction. Understand the concept of interrupts and how and why a processor uses interrupts List and describe the levels of a typical computer memory hierarchy. Explain the basic characteristics of multiprocessor and multicore organization. Discuss the concept of locality and analyze the performance of a multilevel memory hierarchy. Understand the operation of a stack and its use to support procedure call and return. BYU CS 345OS Overview (Chapter 1)6

BYU CS 345OS Overview (Chapter 1)7 Processor Registers User-visible registers May be referenced by machine language Available to all programs - application programs and system programs Data Registers – can be changed by user Address Registers – could be separate from data register Stack Registers – user / supervisor stacks Condition Codes – results of operations Control and status registers May or may not be visible Program Counter (PC) – address of next instruction Instruction Register (IR) – most recently fetched instruction MAR/MBR – memory reference registers Program Status Word (PSW) – condition codes, interrupts, mode Registers

BYU CS 345OS Overview (Chapter 1)8 CPU Registers

BYU CS 345OS Overview (Chapter 1)9 Instruction Execution Registers

BYU CS 345OS Overview (Chapter 1)10 Instruction Execution Registers

Learning Objectives Describe the basic elements of a computer system and their interrelationship. Explain the steps taken by a processor to execute an instruction. Understand the concept of interrupts and how and why a processor uses interrupts List and describe the levels of a typical computer memory hierarchy. Explain the basic characteristics of multiprocessor and multicore organization. Discuss the concept of locality and analyze the performance of a multilevel memory hierarchy. Understand the operation of a stack and its use to support procedure call and return. BYU CS 345OS Overview (Chapter 1)11

Main Routine (synchronous) Interrupt Service Routines BYU CS 345OS Overview (Chapter 1)12 Interrupt Service Routine Interrupt Interrupt Service Routine (asynchronous) Main Routine (synchronous) Interrupt Service Routine (asynchronous) Main Routine (synchronous) Interrupt Service Routine (asynchronous) Main Routine (synchronous)

BYU CS 345OS Overview (Chapter 1)13 Interrupts The interrupt was the principle tool available to system programmers in developing multi-tasking systems! Classes of Interrupts Program: arithmetic overflow, division by zero Execute illegal instruction Reference outside user’s memory space I/O: Timer, DMA Hardware failure Interrupt control Disable during ISR Enable upon exiting Allow Interrupts? Priorities?

Learning Objectives Describe the basic elements of a computer system and their interrelationship. Explain the steps taken by a processor to execute an instruction. Understand the concept of interrupts and how and why a processor uses interrupts List and describe the levels of a typical computer memory hierarchy. Explain the basic characteristics of multiprocessor and multicore organization. Discuss the concept of locality and analyze the performance of a multilevel memory hierarchy. Understand the operation of a stack and its use to support procedure call and return. BYU CS 345OS Overview (Chapter 1)14

Storage Performance BYU CS 345OS Overview (Chapter 1)15 Level1 Name Registers Typical Size < 1KB Implementation Technology Custom memory w/multiple ports CMOS Access time (ns) Bandwidth (MB/sec) 20, ,000 Managed by Compiler Backed by Cache

Storage Performance BYU CS 345OS Overview (Chapter 1)16 Level12 Name RegistersCache Typical Size < 1KB< 16MB Implementation Technology Custom memory w/multiple ports CMOS On-chip CMOS RAM Access time (ns) Bandwidth (MB/sec) 20, ,000 5, ,000 Managed by CompilerHardware Backed by CacheMain

Storage Performance BYU CS 345OS Overview (Chapter 1)17 Level123 Name RegistersCache Main memory Typical Size < 1KB< 16MB<64GB Implementation Technology Custom memory w/multiple ports CMOS On-chip CMOS RAM CMOS SRAM Access time (ns) Bandwidth (MB/sec) 20, ,000 5, ,000 1,000- 5,000 Managed by CompilerHardwareOS Backed by CacheMainDisk

Storage Performance BYU CS 345OS Overview (Chapter 1)18 Level1234 Name RegistersCache Main memory Solid state disk Typical Size < 1KB< 16MB<64GB<1TB Implementation Technology Custom memory w/multiple ports CMOS On-chip CMOS RAM CMOS SRAM Flash Access time (ns) , ,000 Bandwidth (MB/sec) 20, ,000 5, ,000 1,000- 5, Managed by CompilerHardwareOS Backed by CacheMainDisk

Storage Performance BYU CS 345OS Overview (Chapter 1)19 Level12345 Name RegistersCache Main memory Solid state disk Hard disk Typical Size < 1KB< 16MB<64GB<1TB<10TB Implementation Technology Custom memory w/multiple ports CMOS On-chip CMOS RAM CMOS SRAM FlashHard disk Access time (ns) , ,000 5,000,000 Bandwidth (MB/sec) 20, ,000 5, ,000 1,000- 5, Managed by CompilerHardwareOS Backed by CacheMainDisk Disk or tape

Learning Objectives Describe the basic elements of a computer system and their interrelationship. Explain the steps taken by a processor to execute an instruction. Understand the concept of interrupts and how and why a processor uses interrupts List and describe the levels of a typical computer memory hierarchy. Explain the basic characteristics of multiprocessor and multicore organization. Discuss the concept of locality and analyze the performance of a multilevel memory hierarchy. Understand the operation of a stack and its use to support procedure call and return. BYU CS 345OS Overview (Chapter 1)20

Cluster computing Loosely coupled - network Client / server environment Middleware DME, RPC Multi (processor/core) Traditionally, the computer has been viewed as a sequential machine. Multiple control signals Pipelining BYU CS 345OS Overview (Chapter 1)21 Parallelism Symmetric Multiprocessors (SMP) 2 or more identical processors that share resources Integrated OS to control jobs, tasks, files, data elements… High degree of interaction/cooperation between processes Multicore Computers Single piece of silicon (die) Independent processors + levels of cache Intel Core i7 Prefetching

Learning Objectives Describe the basic elements of a computer system and their interrelationship. Explain the steps taken by a processor to execute an instruction. Understand the concept of interrupts and how and why a processor uses interrupts List and describe the levels of a typical computer memory hierarchy. Explain the basic characteristics of multiprocessor and multicore organization. Discuss the concept of locality and analyze the performance of a multilevel memory hierarchy. Understand the operation of a stack and its use to support procedure call and return. BYU CS 345OS Overview (Chapter 1)22

Given: Processor speed is faster than memory speed Execution/data localizes Processor Cache: Contains a portion of main memory Invisible to operating system Used similar to virtual memory Increases the speed of memory Processor first checks cache - If not found in cache, the block of memory containing the needed information is moved to the cache Disk cache, I/O cache, VM cache,… BYU CS 345OS Overview (Chapter 1)23

Two-Level Memory Locality Spatial locality – clustered access Large cache Pre-fetch Temporal locality – recent/repeated access Cache Least Recently Used (LRU) Cache hierarchy BYU CS 345OS Overview (Chapter 1)24

Learning Objectives Describe the basic elements of a computer system and their interrelationship. Explain the steps taken by a processor to execute an instruction. Understand the concept of interrupts and how and why a processor uses interrupts List and describe the levels of a typical computer memory hierarchy. Explain the basic characteristics of multiprocessor and multicore organization. Discuss the concept of locality and analyze the performance of a multilevel memory hierarchy. Understand the operation of a stack and its use to support procedure call and return. BYU CS 345OS Overview (Chapter 1)25

The Call / Return Mechanism BYU CS 345OS Overview (Chapter 1)26 Subroutines Smaller programs. Easier to maintain. Reduces development costs. Increased reliability. Fewer bugs do to copying code. More library friendly. Faster programs. Less overhead.

BYU CS 345OS Overview (Chapter 1)27

Summary…

BYU CS 345OS Overview (Chapter 1)29 What is an O.S.? Not always a clear definition as to what constitutes an O.S. and what is an application CD-Rom Driver Scandisk Internet Explorer Intermediary between the hardware and the users Allocate resources (CPU, Memory, disk space, etc.) between programs and users efficiently Allow the user to conveniently access data and programs Protect the system from incorrect or malicious programs and users Summary

BYU CS 345OS Overview (Chapter 1)30 Hardware Review Elements of a system: · Processor Registers (address, data, control) Instruction cycle (fetch, decode, execute) Interrupts Usually includes hardware and special instructions to help the O.S. manage memory, devices, etc. · Memory Different levels (cache, main memory, disk) Operating system will generally manage memory (both RAM and disk), and move data back and forth as required · I/O Usually use Interrupts, DMA Operating system usually controls use of I/O devices Summary

BYU CS 345OS Overview (Chapter 1)31 Registers Used for frequently accessed items User-Visible registers – Available to the programmer and compiler Data Registers Address Registers (Index, Segment, Stack Pointer) Condition code/flags Control and Status registers – Used to control the processor Program Counter/Instruction Pointer Memory address/data Processor Status Word Debugging registers Temp registers Memory Management registers Summary

BYU CS 345OS Overview (Chapter 1)32 Interrupts Allow I/O devices to get the CPUs attention at regular intervals (Program, Timer, I/O, Hardware failure) Helps the O.S. by reducing the time spent monitoring I/O devices CPU checks for interrupts after each instruction, starts the handler if needed May allow nested interrupts I/O techniques Programmed I/O Interrupt-Driven I/O Direct Memory Access Summary

BYU CS 345OS Overview (Chapter 1)33 Interrupts and I/O Handling and Interrupts: Figure 1.10 (pg 23) Device sends interrupt request to CPU CPU finishes current instruction CPU acknowledges request CPU saves PC and PSW CPU loads PC with the address of the first instruction in the interrupt handler (may get help from interrupt request) Interrupt handler starts, often saves other CPU registers and key values Interrupt handler responds to the device Interrupt handler restores CPU registers and key values CPU restores PC and PSW and resumes previous program Summary

BYU CS 345OS Overview (Chapter 1)34 Memory Varying types of memory Registers, Cache, RAM, Disk, CD Vary in speed, size, cost CPU and O.S. try to keep frequently used data in faster memory Cache – Use a small high-speed memory to improve the apparent speed of a larger low-speed memory Keep track of what is currently being used, load into high-speed memory Replacement Algorithm – What do we get rid of when we run out of memory? Write Policy – How do we respond to modifications? Summary

BYU CS 345OS Overview (Chapter 1)35